Heretofore, a single-crystal is made up to a solid phase in the usual way of a raw material being grown from gas and liquid phases to a solid phase. In the gas and liquid phases, the raw material is heated to evaporate or melted at a high temperature, or are made into a solution with a proper solvent in which the raw material is divided into separate atoms and molecules until it can be made to grow to a crystal.
In the solid phase, a multi-crystal raw material is heated, as its shape is retained, to make a solid phase reaction. In the reaction, it can release distortion energy to grow to a single-crystal. There is a great difference between a solid phase and a gas or liquid phase. As described above, the process of the present invention can obtain a large, complicated precise shape of a synthetic single-crystal unit as it is a method in which a plurality of synthetic single-crystals can be chemically combined to integrate and assimilate together without damaging the crystal structure of the already-grown synthetic single-crystals made up to a solid phase and gas or liquid phase.